A theoretical analysis of the mechanics of the left ventricle has been undertaken in which the myocardium is modeled as a fluid-fiber continuum. The passive and active length-tension relations of papillary muscle are applied to the three-dimensional architecture of the myocardium. The anisotropic elastic behavior is crucial to understanding the contractility of the myocardium, the development of systolic pressure, pumping of blood out of the ventricular chamber, and the flow of blood in the myocardium itself.